Add MkDocs Material documentation site with 40 pages and auto-generated API reference

Sets up a complete documentation website with 7 navigable sections (Home, Getting
Started, User Guide, Architecture, API Reference, Deployment, Development), light/dark
mode, search, code copy, and Mermaid diagram support. API reference pages use
mkdocstrings to auto-generate docs from source docstrings. GitHub Actions workflow
deploys to GitHub Pages on push to main.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/api/learning.md

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+# Learning Module
+
+The learning module implements router policies that determine which model
+handles a given query. Policies range from static heuristic rules to
+trace-driven learning that improves routing decisions based on historical
+interaction outcomes. The module also provides reward functions for scoring
+inference results.
+
+## Abstract Base Classes
+
+### RouterPolicy
+
+::: openjarvis.learning._stubs.RouterPolicy
+    options:
+      show_source: true
+      members_order: source
+
+### RoutingContext
+
+::: openjarvis.learning._stubs.RoutingContext
+    options:
+      show_source: true
+      members_order: source
+
+### RewardFunction
+
+::: openjarvis.learning._stubs.RewardFunction
+    options:
+      show_source: true
+      members_order: source
+
+---
+
+## Policy Implementations
+
+### TraceDrivenPolicy
+
+::: openjarvis.learning.trace_policy.TraceDrivenPolicy
+    options:
+      show_source: true
+      members_order: source
+
+### classify_query
+
+::: openjarvis.learning.trace_policy.classify_query
+    options:
+      show_source: true
+
+### GRPORouterPolicy
+
+::: openjarvis.learning.grpo_policy.GRPORouterPolicy
+    options:
+      show_source: true
+      members_order: source
+
+---
+
+## Reward Functions
+
+### HeuristicRewardFunction
+
+::: openjarvis.learning.heuristic_reward.HeuristicRewardFunction
+    options:
+      show_source: true
+      members_order: source